1. Field of the Invention
The present invention relates to an inkjet printer which ejects ink onto a printing medium to form an image.
2. Description of the Related Art
In inkjet printers according to a related art, small ink droplets are ejected from plural ejection ports disposed in an inkjet head to conduct a printing operation. The inkjet printers according to the related art are classified into a serial head type printer and a line head type printer. The so-called serial head printer conducts a printing operation by a combination of a moving operation in a main scanning direction (the width direction of a sheet) in which an ink is ejected while moving the inkjet head in the main scanning direction, and an operation in which the sheet is moved in a sub-scanning direction. The so-called line head printer includes a line head having a printing width equal to the width of a sheet serving as a printing medium, and conducts a printing operation while relatively moving the line head and the sheet. In a line head printer, particularly, it is not required to move an inkjet head in the main scanning direction of a sheet. Hence, the printing speed can be made higher than that in a serial head printer.
In both the serial head printer and the line head printer according to the related art, in order to obtain an image of an excellent quality, ink ejection from minute nozzles disposed in the inkjet head must be kept in a satisfactory state. Therefore, a restoring operation is conducted to enable the nozzles to adequately eject small ink droplets. Examples of a restoring operation are a purging operation and a wiping operation. In the purging operation, ink in the inkjet head is discharged to evacuate foreign matters or air bubbles staying in ink flow paths. In the wiping operation, an ink ejection surface where ink ejection ports are disposed is wiped to remove excess ink droplets or foreign matters adhering to the ejection surface.
Such a serial head printer has a structure in which the inkjet head can be moved in the main scanning direction. Therefore, the purging operation or the wiping operation can be conducted after the inkjet head is retracted to a region, which is on an extended line in the main scanning direction and is outside the printing region.
However, an inkjet head of the line head type has an ink ejection surface, which is larger than that of an inkjet head of the serial head type. If a printer is configured so that such an inkjet head is horizontally moved to a region outside the printing region and a restoring operation is then conducted, the size of the printer is inevitably increased. In a line head ink-jet printer according to the related art, therefore, a maintenance unit, which conducts a restoring operation, is inserted between the inkjet head and a medium transporting device while an inkjet head is kept to be horizontally fixed, and the restoring operation is then conducted.
JP-A-2002-120386 (see pages 10-11; and FIG. 13) and JP-A-2000-62151 (see pages 5-6; and FIG. 1) disclose techniques of applying a restoring operation on an ink-jet head in a line head printer. In a printer disclosed in JP-A-2002-120386, when a restoring operation is to be conducted, a gap is formed between an inkjet head and a transport belt by moving the transport belt in a direction (downward direction) along which the transport belt is separated from the inkjet head, or by pressing down the upper face of the transport belt on a upstream or downstream side of the inkjet head in the medium transporting direction, and a maintenance unit is then inserted into the gap in a direction perpendicular to the medium transporting direction of the transport belt.
In the technique of JP-A-2000-62151, while one of two rollers around which a transport belt is wound and supported is used as an axis, the transport belt is swung so as to be separated together with the other roller from an inkjet head, thereby forming a space which enables a maintenance unit to face an ejection surface.